Tone control in photography



March 13, 1951 J. A. c. YULE TONE CONTROL IN PHOTOGRAPHY Filed Oct. 9, 1947 ulcl FIG. I.

PRINT PERFECT REPRODUCTION OF ORIGINAL DENSITY 0F ORIGINAL TRANSPARENCY NEGATIVE I DENSITY or ORIGINAL FIG.3.

PEWZUQ JOHN A.C.YULE

INVENTOR IA 4 P DEIISITY 0 ORIGIPIAL BY Z a A TTORNE YS Patented Mar. 13, 1951 UNITED STATES PATENT OFFICE 1 TONE CONTROL IN PHOTOGRAPHY John A. C. Yule, Rochester, N. Y., assignor to. Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application October 9, 1947, Serial No. 778,826 (01. 95-88) 4 Claims.

This invention relates to photography and parand contrast of photographic images.

This application is a -continuation-in-part of YuleU. S. application serial No. 604,351 filed July 11, 1945, now Patent No.'2,541,490, and relates ticularly to a method for controlling the tone particularly to that modification of the original application including making a negative having increased shadow and highlight contrast, and the use of which does not require any other mask.

It is' well known that contrast is. usually lowered in the shadow and highlight portions and I original subject.

It has been proposed, for example, in making 7 masks for color transparencies to have negative contrast in the shoulder portion of the characteristic curve of the mask, that is, to have a reversed shoulder in the mask so that the con-- trast is raised in the low density region corresponding to the highlight of the transparency. In making a mask of this type, two separate exposure and development steps are required. A

process of this type is described, for example, in- I- Morris 2,338,661 granted January 4, 134A.

It is an object of the present invention to provide a novel method for controlling the tone of a photographic print.- A further object is to provide a novel method of increasing the high-l.

light contrast of a photographic reproduction without appreciably decreasing the shadow contrast. Other objects-will appear'from the following description ofmy invention.

These objects are accomplished by exposing to an image, an emulsion capable of giving high contrast, developing it in' a high contrast, low speed developer, and without re-exposure further developing it in a high-speed developer, preferably one giving low maximum density.

In the accompanying drawing,

Fig. 1 is a graph showing the ideal density relations of a negative and' print and the density relations usually obtained, v

Fig. 2 is a graph showing the method of obtain-' ing improved density according to my invention, and I Y Fig. 3 is a graph showing another method of improving the contrastof the print.

As stated above, previous methods of achieving a lowering of-the shoulder of the characteristic curve so that a reversal of the shoulder is produced have depended on a second exposure to the image after the first development has been carried out. For example, in masking color transparencies, a film was laminated to the transparency, exposed, developed and the silver oxidized to silver bromide. A second exposure was then made through the transparency and the emulsion again developed. Those parts of the image which had been'formed during the first development were now less sensitive so that a reversal of the shoulder was produced.

My novel method,.which eliminates the second exposure, may be carried out as follows:

After exposure, the film'is developed in a blackand-White developer which gives low speed and high contrast. Development is then continued in a color developer which gives a relatively high emulsion speed. The silver is then bleached to a soluble silver salt and the silver salts are removed by fixing, leaving a" dye image having a reversed shoulder portion.

The mechanism of this process is as follows: During the first development, those regions which have received the greatest exposure are almost completely developed so that they will not develop further in the color developer. During the second development the regions which have received somewhat less exposure and which are unaffected by the first developer, develop to a dye and silver image. The regions which have received least exposure do not develop appreciably even in the second developer.

= original which may be a transparency, a print,

or the original subject. If the density of the original is compared with the density of the positive reproduction, the curve should be a straight line since at every point the density of the positive reproduction should be the same as the density of the original. In one type of negative represented by curve N, the curve is a straight line of the opposite slope. Curves for negatives obviously do not meet this requirement but depart from the straight-line relationship in varying degrees. had perfect straight line characteristics of propriate contrasts, a perfect result might be If negative and positive materials achieved. But since photographic materials do not meet. these requirements the typical positive curve instead of being a straight line as at T is generally a curve such as P indicating that shadow and high-light portions have lost contrast and the intermediate tones have increased in contrast. The problem, therefore, curve P closer to curve I.

This result is accomplished accordingto.

istob the ring

one

modification of my invention by the provision of the dye mask made as described above. Assn in Fig. 2 the dye mask obtained by my process may have the density relationships illustrated by the curve M. The original transparency or .positive print which should theoretically be;

the

tained from it is again indicated by the straight- -line curve Twlfthe mask; having -the.;dens ity relationship. represented by Mis registered with -the original .transparencysuch as a colortrails' parency represented by curve T, the .combina tion gion. Ihe intermediate tones-represented by the - portion b of the curve. will have .decreased contrast, this region representing theintermediate tones of the-transparency. In the shadow portions representedby c of the-curve. T+l\/l,..there.is no change-in contrast. -When-this combination of transparencyand mask is printed, .anincrease in contrast in thehigh-light-regions .and a decrease in contrast in the intermediate tones will be tained. 1

The masking-image usedaccording to my invention may be obtained in the following way.

A film capable of giving high contrast such as Eastman Kodalith film is exposed under-a transparency and is developed--for --l% ---to-2 minutes at 68 F. in a developer of the following composition.

.jel-lydroquinone -.;.Sodium sulfitp;

Potassium metabisulfite --Boricacid-" -Potassium bromide i 1,6 -"-Para-formaldehyde Q. 7.5

Water to 1 liter.

- This developer is chosen because of -low..emulsion speed and high contrast-which.it..produces. If a longer reversal scale and lower reversal contrast is desired, aweak alkaline hydroquinone de- *-veloper strongly restrained by. means of antifoggants-may be used. A developerv .produ a gamma of the order of l to 6 is satisfactory in most cases.

cing

I The film is thenrinsed-in water andtransferred directly to a developer having the following com- Grams Sodium metaborate 120 Sodium hydroxide l8 l-p-nitrophenyl-3-methyl-5-pyrazolone 36 5 Tamcl NNO (Rohm & Haas C0.) 5

Water to make 4 liters.

For use, take 1 part Af4 parts B, 5 parts water. :3 The film is developed for one minute in the color developer and is then transferred to an alkaline .potassium bromide stop bath of the following composition:

. Grams .Bqta siumb mid V Sodium carbonate 5 Sodium sulfates-ii 5 Water to make 1 liter.

After three minutes in the stop bath, the film is placed in a bleach bath of the following com- 20 position:

Water to 1 liter.

il'ii iiiieth s'ri ieii' jinb ing bath' of following composition:

Sodium .thiosulfate grams 240 Sodiumlsu1fite ..s do -l5 ..Acetic acid (28% solution) --.-e.-.c "i8 --Boric--acid -4 rams 37.5 :Potassium al um do 15 Water to make 1 liter.

An image dejnthisl way isjusruifror; skeina assassins-$03 3 es l' 'h o l t as 1A ..-bad1y ..Jmderexppsed egativeflxiiiay. be saved by ,combining it withflillal OfItliis typewh'ich will 40 correct the tone rendering without'l decrasir'ig athe contrast. The. pro is Y also valuable in making a mask ior a e; to. increaselhighli h con ra tn. 'e m i h f a photographic nton apcr'by photomechanical ii -methods, where ht ontrasltjis usually lacking, :a; tone correct n i maskfmade in the wca raa el tel m iiififieim fifi y h dethe. original print... By tl e usecf couplers produc- -ing. effect ively a neutratgra ageas described amEyansandflansonjl. Batent 2 ,'l93,0,23, the

process may be used for masking colortransparencies-;.e..

.lnusing the process for mask g in in. ontras o mi sh qwsa g 65 med b pr ce s th t; th j .nnegative part of the ch racteri'sticlbdfl as. a shor.t ,sca1e. g {Th -is; is chieved by adjusting. the .developerscomposition and ti so that 1ess;.-;difierence in, emulsion sp edsfjis 50-. produced; by the. .two QGY81QQGI|SJ The. ,.p rocess .may. also be combinedwith thatgivingitheS abat- I .tier effect to give reversal of botl ends iofIthe .scale.. This isdoneby givinga further uni-form xp e afie e.. ecenddetel pm s to. l ht- 55 the color most str0ne1Y'.-a bsorbed by the y' 'an then continuing. t hedevelopi nent. Special emulsions; and. dBVe1QPB iad i t .e e n creased. Sabattier oeiiect inayl be ll fid- Fi made in this way would correct for bothtoe Sand 70.shoulderot the image w t w h it. combined and-it is articular .adra ta cusltp add ame amount of non-coupling developer 'suclr gas cN-benzyl-peamino phengl to. the color developer. This gives a 1owermi imumd r i'qy pe we tb negative part and the Sabattier reversal part of the curve. Sabattier reversals carried out in the conventional manner have a high minimum density.

According to one modification of my invention, a negative having increased shadow and highlight contrast is made and the use of this image does not involve the use of any mask. My method produces a change in the shape of the characteristic curve of the negative material which effects an increase in the shadow and highlight contrast of the print made from it. Previous attempts to produce emulsions which will give this type of curve have not furnished increased contrast at both ends of the scale. Moreover. such films hav been found to be unstable since on age, that part of the emulsion which was responsible for the shoulder contrast lost speed at a difizerent rate from the rest of the emulsion.

.In order to correct for the characteristic curve of the printing paper used the curve of the negative should be a mirrorimage, rotated through 90", of the curve of the paper, that is, substantially as shown in Fig. 3 curve N3. This curve can be displaced horizontally or vertically by variations in exposure times and can hav a shoulder. This curve is regarded as the sum of two simple curves, the first characterized by high contrast and low speed, the second by high speed and low maximum density.

According to this modification of my invention a silver halide emulsion capable of giving high contrast is exposed to the original, which may be a transparency, a print, or original scene and isdeveloped in a developer which gives high contrast and low speed. This develops the highlights only and the emulsion is then transferred, preferably after an intermediate wash, to a developer which gives high speed and low maximum density. A N-benzyl-p-aminophenol developer is satisfactory.

The effect of this procedure in increasing shadow and high-light contrast is illustrated by the curves of Fig. 3 of the drawing. As shown therein, the original subject or the ideal positive reproduction obtained from it is indicated by curve T. According to normalprocedure a negative image represented by curve N1 is obtained. This negative would produce a positive P1 having low contrast in the shadow and especially the highlight portions as indicated by the slope of the curve P1. According to my novel method, th first development in the high contrast developer produces a negative image having the characteristics indicated by the curve N2, in which the highlights only are recorded. The second development in th high speed developer produces the curve N3. The high contrast in the highlights and shadows of this negative compensates for the low contrast ofthe toe and shoulder of the positive material, so that the positive printed from this negative has the density relationships indicated by curve A. This curve approaches the ideal curve T, the contrast in the shadow and high-light portions having been increased considerably and the contrast in the intermediate tones decreased.

The procedure for obtaining a negative image having the improved characteristics referred to above may be as follows.

An exposure to the original is made on a highcontrast emulsion such as Eastman Kodalith Orthochromatic Film. This exposure must be such that the highlights only will be developed inth first development while sufficient shadow detail appears during the second development. With two 35-ampere whit flame arcs at a distance of 5 feet from the copy, 1:1 magnification, an exposure of about 20 seconds at f.22 will b required.

The emulsion is then developed in the high contrast developer referred to above, whose action has been retarded by the addition of 1 part of the following restrainer to 2 parts of developer:

Sodium sulfate (desiccated) grams 180 Potassium bromide do Acetic acid (28% solution) cc Water to make 1 liter.

The film is developed by inspection until the extreme highlights just go black. If the exposure was correct, this will take place in about 3 minf' utes at 68 F. The film is then rinsed for five seconds in a stop bath of the following formula:

Water liter 1 Acetic acid (28% solution) cc 48 The film is then washed in water at to F. I

for 25 seconds and the development continued for 3 minutes at 68 F. in a developer of the following composition:

N-benzyl p-amino-phenol hydrochloride grams 1.25 Sodium sulfite do 10 Sodium metaborate do 15 Potassium bromide do 2 Benzotriazole (1% solution) cc 20 Water to 1 liter.

The film is immersed in an acetic acid stop bath of the formula stated above for a few seconds and fixed in the fixing bath formula given above. It is then washed and dried. The manner of using this image will be apparent from the above description of my invention. For perfect duplication of a print, using a given printing paper, a, constant exposure and constant processing conditions are theoretically required, however, occasionally it is desirable to alter contrast in copying, for example, a fiat print. This may be done by variation of the first develop- 1 I must have a contrast of at least 3, and can be ashigh as 15, to compensate for the toe of the particular printing paper. It is estimated that for the useful range of the invention the desired contrast is produced when operating at somewhat less than one-fifth of the maximum speed of the film emulsion. In the drawings the maxi mum M speed of the emulsion used would be represented by a curve to theright, of Fig. 3

An emulsion satisfying these requirements is contemplated for use in my invention.

It is apparent that, depending upon the subject and the printing paper, the contrast can be In a typical case, a print to be copied, when reproduced by conventional copying methabove 3.

ods resulted in a picture, when printed with white borders, in which the high-lights lacked con When attempts were.madetmincrease: printing. 1'

time. =.to.:get betterdetail. in; the whites; the result;

was fog. onithe print; borders. When the negative was made according to my invention thespri-nthad .all the detail of the-original subject, in fact, appeared .to have better-quality than-the; original.

Incase, it isdesiized to printontoa lows-contrast:

paper, ofjthe'chloridetype. I may operateat a developer speed diiferential of as high as 15 and a contrastinthe firstdeveloper of about whereby, an accurate copy "of an' original is obtained without change in contrast relative to tho'originalj subject.

As is apparent, the relative emulsion speeds producedby the two: developers is important. Forexam-ple, in copying a very flat orstained,

original, I it. may be: desired 1 to :"iHC-I'EELSE the -:con-

tras t-;.and; the second developer ;would have a speed of about 4 to 5 times that of the ii1'st.

When making'a negative of'atransparenoy of high contrast; the diiference' in developer speeds would be -oftheoorder of .-50.to 160 times.

Myiiprocess. aiso requires that the secondde-- veloperbecapable of producing with the emulsion specified a maximum density of ,atleast :1 less than is ordinarily obtainable with said emulsion.

That is, the emulsion is capable of giving a density of: about 5 when fully exposed and developed;but "the useful range for my invention In place of the seconddevelopencontaining...

an aminov phenol developing agent, I can use a p-phenylene diamine developing agent such-as p-diethylamino-aniline,- the formula containing thexsame producing an emulsion speed and.

maximum. density in the range specified.

W here'I refer in the claims to exposure .to an image, it will be understood that I intend to in-.- elude exposure to atransparency, a print, or the.

original subject.

It-will be understood that the examples included herein are illustrative only and that my invention is to be taken as limited only by the scope of the appended claims.

What I claim is:

l. The method of making a negative photographic image ,having increased shadow and highlight contrast which comprises exposing to animage a silver halide emulsion layer giving a contrast of from 3 to when developed to less than one-fifth its maximum speed in a developer having the composition:

Grams Hydroquinone 22.5 Sodium sulfite Potassium metabisulfite 2.6 Boric acid 7.5 Potassium bromide 1.6 Paraformaldehyde 7.5

Water to 1 liter.

whose action has been retarded by the addition an is less than 5 or preferably a maximum density 8 f of .oneypart gof the following; restrainer to two i partsl'ofl said developer:

Sodium sulfate (dessicated) grams Potassium bromide do; 10 Acetic acid 28 solution) cc 32 Water tol liter.-

developingsaid emulsion to a contrast of'from 3 to 15 at less than one-fifth the maximumspeed of. said. emulsion, andwithout fogging residual silver halide developing said emulsion in a second developer'giving an emulsion speed of from 5 to 10.0 times that of said first-mentioned developer; and a maximum density between 0.5 and 2.0.

2. The method of making a negative photographic image having increased shadow and high-- light, contrast. which comprises exposing toan image a silver'halide emulsion layer giving a con-"-- trast of from 3 to 15 when developed to less-than one-fifth its maximum speed in a developer-hawing the composition:

Grams Hydroquinone 22:51. Sodium sulfite 30 Potassiumlmetabisulfite 2.6-. Boric acid 7.5 Potassiumbromide 1.6 Paraformaldehydep 7.5

Water to 1 liter.

whose action has'been retarded by the addition of one part of the following restrainer to twoparts of said developer:

Sodium sulfate (de'ssicated). p grams 180 j Potassium. bromide do 10' i Aceticacid (28%.s0lution). cc ,,32'.

Water to 1 liter.

developing said-emulsion to a contrast of from 3 to 15 at less-than one-fifth the maximum speed of said emulsion, and without fogging resid-i. ual silver halide developing saidemulsion in a second developer giving an emulsion speedof approximately 5 times that of said .first-Jnentioned' and a maximum density between-.05 and 2.0.

3. The method of making a negative phot0. graphicimage having increased. shadow and) highlight contrast. which comprises exposing tov an image a silverhalide emulsion layer givingza contrast of from. 3 to 15 when developed to less than one-fifth its maximum speed in a-de-p; veloper having the composition:

Grams I-Iydroquinone 22.5" Sodium sulfite 30 Potassium metabisulfite 2.6 Boric acid 7.5' Potassium bromide 1.6 i Paraforma'ldehyde 7.5

Water to '1 liter.

whose action has been retarded by the addition of one part of the following restrainer to two parts of said developer:

Sodium sulfate (dessicated) "grams. 180) I Potassium-bromidev d o 4 10 Acetic acid,(28% solution) cc 32 Water to 1 liter.

developing said emulsion to a contrast of from 3 to 15 at less than one-fifth the maximum speed of saidemulsion, and without fogging residual. silver halide developing said emulsion in a second. developer giving an emulsion speed of from some...

.9 100 times that of said first-mentioned developer and a maximum density between 0.5 and 2.0.

4. The method of making a negative photographic image having increased shadow and highlight contrast which comprises exposing a silver halide emulsion layer to an original, developing the regions of greatest exposure of said exposed layer in a developer having the composition:

Grams Hydroquinone 22.5 Sodium sulfite 30 Potassium metabisulflte 2.6 Boric acid 7.5 Potassium bromide 1.6 Paraformaldehyde 7.5

Water to 1 liter.

whose action has been retarded by the addition of one part of the following restrainer to two parts of said developer:

Sodium sulfate (dessicated) grams 180 Potassium bromide -do 10 Acetic acid (28% solution) cc- 32 Water to 1 liter.

until the extreme highlights just go black, rinsing said layer for about five seconds in an acetic acid stop bath, and then immediately, without fogging residual silver halide, developing said layer'for three minutes at 68 F., in a developer of the following composition:

N -benzyl p-amino-phenol hydrochloride grams 1.25 Sodium sulfite -do 10 Sodium metaborate do 15 Potassium bromide do 2 Benzotriazole (1% solution) cc 20 Water to 1 liter. to produce a negative image having high contrast in the highlights and shadows and lower contrast in the intermediate tones.

JOHN A. C. YULE.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS of the Society of Motion Picture Engineers, vol. 32, April 1939, pp. 412-418. 

1. THE METHOD OF MAKING A NEGATIVE PHOTOGRAPHIC IMAGE HAVING INCREASED SHADOW AND HIGHLIGHT CONTRAST WHICH COMPRISES EXPOSING TO AN IMAGE A SILVER HALIDE EMULSION LAYER GIVING A CONTRAST OF FROM 3 TO 15 WHEN DEVELOPED TO LESS THAN ONE-FIFTH ITS MAXIMUM SPEED IN A DEVELOPER HAVING THE COMPOSITION: 